"I know nothing," when it comes to insulators. I mainly collect fruit jars but sometimes I see an insulator that catches my eye enough to buy. This is a W. E. MFG. CO. CD126.4 in a pale aqua. There is no damage to the insulator except a couple of minor wire rubs in the groove. How uncommon are these?

The front is embossed,
(dome)
W. E. MFG. CO.
(skirt)
PATENT
APPLIED FOR ( over DEC. 19. 1871 you can still see several of these characters )

The reverse is embossed,
(dome)
W. U. ( for Western Union )